Arrangement for the separate regulation of the tube currents for a plurality of x-ray tubes



June 17, 1969 oo 3,450,880

ARRANGEMENT FOR THE SEPARATE REGULATION OF THE TUBE CURRENTS FOR APLURALITY OF XRAY TUBES Filed Oct. 23, 1965 Sheet J W3 s V I FIQE-JZ x1I I 'qul M1 HT1 7 w ST1 B1 i v M W ST INVENTOR June 17, 1969 B. MOO3,450,880

ARRANGEMENT FOR THE SEPARATE REGULATION OF 'THE TUBE CURRENTS FOR APLURALITY OF X-RAY TUBES Filed Oct. 23, 1965 Sheet 3 of s X }-r i I Flg3 ?1 I I on. l D w 5T1 l vPR' A XZ 2 HT 5T2 z FRZ LT HT T Q1 x1 c I l f1 1 ST l 1 q R1 L I N V E NTO R flea/v0 MopK ATTORNEYS June 17, 1969 53,450,880

ARRANGEMENT FOR THE SE'P .MOO ARATE REGULATION OF THE TUBE CURRENTS FORA PLURALITY OF X-RAY TUBES Filed Oct. 23, 1965 Sheet 3 of 3 IN VE NTOR5ZUA/O Mack BY M ATTORNEYS United States Patent Int. Cl. nos 1/70 US.Cl. 250-94 8 Claims ABSTRACT OF THE DISCLOSURE An arrangement for theregulation of individual X-ray tubes which are fed from a singlehigh-voltage source and which X-ray tubes have their anodes connected toground potential. A setting member is connected with each of the X-raytube circuits and responsive to the X-ray tube current to control afilament transformer also associated with each X-ray tube. A transduceris connected in series with the cathode of each of the X-ray tubes forsensing the current flow through the X-ray tube. Connected to each ofthe transducers is a regulating device which, in turn, is connected tothe setting member for controlling the current flow through the X-raytube in response to a value selected by the setting member.

A certain measured value has been necessary for an automatic regulationof the X-ray tube current, and dependent on the tube current, for anX-ray apparatus known in the past. The actual value of the regulatingmagnitude is tapped from a resistor situated on the ground side of thehigh-voltage circuit. This relatively simple method for obtaining theactual value of the regulating magnitude on the ground side of thehigh-voltage circuit is possible only in the operation of one X-raytube. Since in general the X-ray tubes in question operate with groundedanodes and the anodes are cooled with water, a shunt circuit is providedfor the cooling in parallel operation of several tubes, making itimpossible to exactly obtain the tube current of the individual tube onthe grounded anode side.

There is a possibility of circumventing this difficulty by arranging anequal number of secondary windings in the high-voltage generator forseveral X-ray tubes. The winding end not connected to high-voltagepotential can then be connected to ground via a resistor. The resistorcan serve as a measuring resistor for a current proportional voltagevalue. This solution requires, as already mentioned, a separatesecondary winding on the highvoltage transformer for each of the tubesto be operated.

In order to avoid this expenditure and not have the main part of theregulating device for the tube currents connected to high-voltagepotential, a system for the separate regulation of the tube currents ofseveral X-ray tubes fed from a high-voltage generator is constructedaccording to the invention in such a way that only one well insulatedpart of the measuring sensors and of the setting members of theregulating devices for the tube currents are placed on high-voltagepotential, and all the other members of the regulating devices areplaced at ground potential.

By means of the system according to the invention, the shunt circuitsexisting through the water cooling of the grounded anodes becomeinconsequential for the measuring of the individual tube currents,because the actual value of the regulating magnitude is taken on thehigh-voltage side which is connected to the cathodes of the X-ray tubes.Nevertheless, insulation difficulties are avoided, because a separationis made between highvoltage potential and ground potential in themeasuring sensor, so that the greater portion of the regulating circuitis connected to ground potential.

A heating transformer can be used for heating the cathode of the X-raytube, as a setting member for the regulating device. The primary voltageis delivered from the regulating device. The cathode heating is operatedwith the voltage from the secondary winding. In the case of X-ray tubeswith a Wehnelt cylinder or a control grid, these electrodes can serve assetting members for regulation of the tube current.

In general, it is expedient to arrange grounded potential screensbetween the high-voltage conducting and the ground side parts of theregulating magnitude.

In different examples of operation of the invention, various measuringsensors are used. Thus, a transducer whose direct current winding is inthe high-voltage circuit of the individual X-ray tube can serve as ameasuring sensor. The direct current winding is highly insulated withrespect to the core of the transducer which is connected to groundpotential.

In another example of the operation of the invention, a magnetic fielddependent resistor which is arranged in the air gap of a magnet yokewhose field winding lies in the X-ray tube circuit can serve as ameasuring sensor. The field windings are highly insulated with respectto the magnet yoke, which is connected to ground potential.

In another example of the operation of the invention, a high-voltagedivider is arranged on the high-voltage side. One member of this divideris formed by a resistor controlled by the X-ray tube current. It ispossible to tap a control voltage for the regulation of the X-ray tubecathode heating on the low-voltage side of the divider. The resistor inthe high-voltage divider circuit can be a high vacuum diode heated bythe X-ray tube current and controlled by the tube current. Anothersolution is to provide a grid-controlled high vacuum tube whosecathodeanode interval serves as a controlled resistor. One control gridof this tube is connected to a measuring resistor in the X-ray tubecircuit. A transistor can be used in place of the grid-controlled tube.The emitter collector interval serves as a resistor dependent on theX-ray tube current.

The invention is explained in detail with the aid of five figures whichrepresent examples of the operation. In the figures, like structuralparts are provided with the same reference characters.

FIGURE 1 is a schematic wiring diagram of an X-ray circuit according tothe present invention;

FIGURE 2 is a schematic wiring diagram showing an alternate form of theX-ray circuit of FIGURE 1;

FIGURE 3 is a schematic wiring diagram showing an alternate form of theX-ray circuit of FIGURE 1;

FIGURE 4 is a schematic wiring diagram showing still another alternateform of the X-ray circuit of FIGURE 1; and

FIGURE 5 is a schematic wiring diagram showing yet another form of theX-ray circuit of FIGURE 1.

In FIG. 1, a high-voltage transformer is designated with T which isconnected to a rectifier bridge G1, A capacitor C is provided as afilter. The plus pole of the high voltage bridge is grounded. The minuspole of the bridge is connected via windings W W and W of transducers TKto TK with the cathodes of three X-ray tubes X to X The anodes of theX-ray tubes are connected to ground potential. Control windings of thetransducers TK to TK are connected to regulators R to R The outputs ofregulators R to R via setting members ST to ST regulate the primarycurrent in the primary windings of heating transformers HT t-o HT forthe heating 3 of the cathodes of the X-ray tubes. The number of X-raytubes to be operated in parallel in this manner is dependent only on thepower of the high-voltage generator.

In FIG. 2, magnet yokes M and M whose exciter winding or field windingis traversed by X-ray tube current on the high-voltage side, take theplace of the transducers. The iron of the yoke, as well as the core ofthe transducers, is grounded in the operation according to FIG. 1. Fielddependent resistors FW and FW which are components of a bridge circuit Bor B respectively, are arranged in the air gap of the magnet yokes. Theoutput voltages of the bridges control via setting members 5T and 8T(again in accordance with the operation as shown in FIG. 1) the primarycurrent of heating transformers HT, and HT which supply the heatingpower for the cathode heating of the X-ray tubes. The secondary windingsof the heating transformers are connected to high-voltage potential andare highly insulated against the cores of the heating transformersconnected to ground potential.

In the examples of the operation according to FIG. 3, the input voltagefor the regulators R and R is tapped at resistors P and P respectively.These resistors ar a component of a high voltage divider circuit, havingvacuum diodes D and D connected to high voltage. The cathodes of thevacuum diodes D and D are heated by the X-ray tube currents. Theinternal resistance of the diodes is thus dependent upon the X-ray tubecurrent. Therefore, the input voltage for the regulator, which is tappedat the resistors P and P becomes dependent upon the X-ray tube current.

In a futher example of the operation according to FIG. 4, the vacuumdiodes are replaced by grid-controlled vacuum tubes R6 and R6 Thecontrol voltage of these tubes is tapped at resistors Q and Qrespectively, which carry the X-ray tube currents. A special heatingtransformer HT provides the heating power for the tuges R6 and R62- Inan example of the operation execution according to FIG. 5 thegrid-controlled high vacuum tubes are replaced by transistors Tr and Tras components of high voltage divider circuits. The emitter-collectorregions of the transistors serve as resistors dependent on X-ray tubecurrent in the voltage dividers. The control voltage for the transistorsis regulated by means of resistors Q and Q connected in the X-ray tubecurrent circuit. In the examples of the operation according to FIGS. 2to 5, more than two X-ray tubes can be operated in parallel on ahighvoltage generator.

The regulators R R and R may be of any suitable design to produce acontrol voltage which is maintained in accordance with the settingmembers 5T ST and ST;; respectively. One such regulating device is shownin the patent to W. E. Splain 3,325,645 and is designated MA stabilizer.Additionally, the setting members ST ST and 8T are used to select thedesired amount of current flow through each of the associated X-raytubes X X and X respectively. One such setting member which can be usedin accordance with the principles of this invention is shown in thepatent to C. W. Clapp et al. 2,810,838. Accordingly, neither theregulating members R R and R nor the setting devices 8T ST and 8T inthemselves form a part of this invention.

Changes may be made within the scope and spirit of the appended claimswhich define what is believed to be new and desire to have protected byLetters Patent.

I claim:

1. An arrangement for the separate regulation of a plurality of X-raytubes which are operatedfrom a single high-voltage source, comprising: ahigh-voltage source; a plurality of X-ray tubes each having their anodeconnected to ground potential and their cathode connected to saidhigh-voltage source, each of said X-ray tubes having a heater filament;a plurality of filament transformers, each filament transformer havingits secondary winding connected to the heater filament of its associatedX-ray tube, and further having a primary winding; a control circuitconnected to each of said X-ray tubes to control the amount of heatingcurrent applied to the associated heating filament, each of said controlcircuits including, electromagnetic sensing means including anelectromagnetic transducer having a winding which is insulated fromground potential and connected in series with the cathode circuit of theassociated X-ray tube operative to sense the actual amount of directcurrent passing through said winding and thus through the X-ray tube, asetting member for selecting a desired amount of current to pass throughthe associated X-ray tube, regulator means connected between saidsensing means and said setting member to compare the actual amount ofcurrent passing through the associated X-ray tube with that of thedesired amount of current thereby producing a control voltage, andcircuit means connecting the primary winding of said filamenttransformer with said regulator means, whereby, said control voltagewill control the amount of heating current applied to the heaterfilament of the associated X-ray tube.

2. An arrangement for the separate regulation of a plurality of X-raytubes which are operated from a single high-voltage source, comprising:a high-voltage source; a plurality of X-ray tubes each having theiranode connected to ground potential and their cathode connected to saidhigh-voltage source, each of said X-ray tubes having a heater filament;a plurality of filament transformers, each filament transformer havingits secondary winding connected to the heater filament of its associatedX-ray tube, and further having a primary winding; a control circuitconnected to each of said X-ray tubes to control the amount of heatingcurrent applied to the associated heating filament, each of said controlcircuits including, sensing means connected in series with theassociated X- ray tube for sensing the actual amount of direct currentpassing through the X-ray tube, a setting member for selecting a desiredamount of current to pass through the associated X-ray tube, regulatormeans connected between said sensing means and said setting member tocompare the actual amount of current passing through the associatedX-ray tube with that of the desired amount of current thereby producinga control voltage, circuit means connecting the primary winding of saidfilament transformer with said regular means, whereby, said controlvoltage will control the amount of heating current applied to the heaterfilament of the associated X-ray tube, said sensing means being formedby a field winding of a magnetic yoke and further including a magneticfield dependent resistor responsive to the magnetic field produced bysaid magnetic yoke, said magnetic field dependent resistor beingconnected to said regulator means.

3. An arrangement for the separate regulation of a plurality of X-raytubes according to claim 2 wherein said magnetic yoke is connected toground potential.

4. An arrangement for the separate regulation of a plurality of X-raytubes which are operated from a single high-voltage source, comprising:a high-voltage source; a plurality of X-ray tubes each having theiranode connected to ground potential and their cathode connected to saidhigh-voltage source, each of said X-ray tubes having a heater filament;a plurality of filament transformers, each filament transformer havingits secondary winding connected to the heater filament of its associatedX-ray tube, and further having a primary winding; a control circuitconnected to each of said X-ray tubes to control the amount of heatingcurrent applied to the associated heating filament, each of said controlcircuits including, sensing means connected in series with theassociated X-ray tube for sensing the actual amount of direct currentpassing through the X-ray tube, a setting member for selecting a desiredamount of current to pass through the associated X-ray tube, regulatormeans connected between said sensing means and said setting member tocompare the actual amount of current passing through the associatedX-ray tube with that of the desired amount of current thereby producinga control voltage, circuit means connecting the primary winding of saidfilament transformer with said regulator means, whereby, said controlvoltage will control the amount of heating current applied to the heaterfilament of the associated X-ray tube, said sensing means including thefilament of an electron tube connected in series with the direct currentof the associated X-ray tube, the conduction of said electron tube beingproportional to the current passing through said X-ray tube, and avoltage divider connected in series with said electron tube, the outputof said voltage divider being connected to said regulator means.

5. An arrangement for controlling the separate regulation of a pluralityof X-ray tubes according to claim 4 wherein said electron tube is adiode.

6. An arrangement for the separate regulation of a plurality of X-raytubes which are operated from a single high-voltage source, comprising:a high-voltage source; a plurality of X-ray tubes each having theiranode connected to ground potential and their cathode connected to saidhigh-voltage source, each of said X-ray tubes having a heater filament;a plurality of filament transformers, each filament transformer havingits secondary winding connected to the heater filament of its associatedX-ray tube, and further having a primary winding; a control circuitconnected to each of said X-ray tubes to control the amount of heatingcurrent applied to the associated heating filament, each of said controlcircuits including, sensing means connected in series with theassociated X-ray tube for sensing the actual amount of direct currentpassing through the X-ray tube, a setting member for selecting a desiredamount of current to pass through the associated X-ray tube, regulatormeans connected between said sensing means and said setting member tocompare the actual amount of current passing through the associatedX-ray tube with that of the desired amount of current thereby roducing acontrol voltage, circuit means connecting the primary winding of saidfilament transformer with said regulator means, whereby, said controlvoltage will control the amount of heating current applied to the heaterfilament of the associated X-ray tube, said sensing means including aresistor connected in series with the current passing through theassociated X-ray tube, and a variable conduction device connected tosaid resistor, and a voltage divider network connected to said variableconduction device, said voltage divider network having the outputthereof connected to said regulator means.

7. An arrangement for the separate regulation of a plurality of X-raytubes according to claim 6 wherein said variable conduction device is anelectron tube.

8. An arrangement for the separate regulatiOn of a plurality of X-raytubes according to claim 6 wherein said variable conduction device is atransistor.

References Cited UNITED STATES PATENTS 2,810,838 10/1957 Clapp et a1.250-103 2,838,681 6/1958 Graves et a1. 250 94 2,864,958 12/ 1958Morrison 25094 3,325,645 6/1967 Splain 25O103 RALPH G. NILSON, PrimaryExaminer. A. L. BIRCH, Assistant Examiner.

US. Cl. X.R.

